The lower leg contains 10 different muscles. The calf comprises two muscles: soleus and gastrocnemius. Other lower leg muscles include tibialis anterior (ankle extension); tibialis posterior (ankle inversion); peroneus longus and peroneus brevis (ankle eversion); and the toe flexors and extensors (flexor digitorum longus, flexor hallucis longus, extensor digitorum longus, extensor hallucis longus). In this post you’ll find out what every serious bodybuilder or even a regular gym goer should know about his soleus muscle: location, size, shape, function, origin, insertion, innervation, palpation, etc. Because this muscle contracts with considerable force as it continually counters the force of gravity to keep the body upright during ambulation (e.g., walking, running, hiking) you should really dedicate some extra time to get to know this important muscle in more detail.
Muscle location and size
The soleus is a broad but flat muscle that connects to the Achilles tendon. This muscle is located partially underneath and partially below the gastrocnemius (the most externally visible muscle). It sweeps out to the sides and over across the shins. Therefore, the soleus muscle is also visible and palpable on the sides of the Achilles tendon, usually more so on the lateral side.
3D preview of the soleus muscle
Differences between the soleus and gastrocnemius muscle
First and foremost, they differ in shape and size. Giving your calves their characteristic shape is the gastrocnemius, the larger (upside-down heart- or diamond-shaped) calf muscle at the rear of the lower leg. It is also the most visible of the two muscles. Lying beneath the gastrocnemius is the soleus, a smaller, flat muscle. It has much less mass than the gastrocnemius.
When it comes to just looks, we’re most concerned with the gastrocnemius, but a properly developed soleus “props up” the gastrocnemius, making it look more impressive.
Other than size, there is a great difference between the gastrocnemius and the soleus. Only the gastrocnemius is a multijoint muscle. This particularity will have serious repercussions for every calf exercise. Because it is a single-joint muscle, the soleus participates in all calf exercises whether or not the leg is bent. However, the more you bend your leg, the less the gastrocnemius will be able to assist with that movement. This is why exercises in which the leg is bent at 90 degrees will isolate the soleus and neglect the gastrocnemius.
Last but not least, the gastrocnemius muscle is made up of mostly fast twitch (Type II) muscle fibers. This type of muscle fibers forcefully contract to produce explosive movements, but experience rapid fatigue. These fibers are crucial for heavy weight training and sprinting. Soleus muscle, on the other hand, primarily consists of slow twitch (Type I) muscle fibers which are highly fatigue resistant. This means that we use them for aerobic and endurance-type activities that range from maintaining posture, walking, jogging, or long-distance running. Therefore, these type of muscle fibers cannot produce the forceful contractions required for creating fast and powerful movements.
The function of the soleus muscle
Both calf muscles cause plantar flexion of the ankle (flexes the foot at the ankle joint), the movement required to stand on tiptoes. This movement is similar to stepping on the gas in your car. The relative contribution of the two calf muscles depends on the angle of knee flexion. Gastrocnemius is the prime mover when the leg is straight, and soleus becomes more active as the knee bends. Note that gastrocnemius crosses both the knee and ankle joints and therefore serves a double function, causing knee flexion and ankle flexion.
Therefore, the soleus muscle helps out the gastrocnemius when your knee is bent and you need to raise your heels up, like when you’re sitting at the movies and you realize that you just stepped in gum.
Soleus muscle origin, insertion, innervation
The soleus muscle arises (originates) from the head of the fibula and the posterior surface of the tibia and joins with the fibers of the gastrocuemius to insert into the Achilles tendon where it attaches to the calcaneus. Both of these muscles attach to the heel via the Achilles tendon.
Therefore, gastrocnemius and soleus muscles share a common tendon, the calcaneal tendon. This tendon may also be
called the calcanean tendon or the Achilles tendon. It inserts into the calcaneus, or heel bone. By acting together, these muscles serve as powerful flexors (plantar flexion) of the foot.
In short:
- Origin: Head and proximal shaft of fibula, and adjacent posteromedial shaft of tibia
- Insertion: Calcaneus via calcaneal tendon (with gastrocnemius)
- Innervation: Sciatic nerve, tibial branch (S1—S2)
Best exercise to target your soleus muscle (target training)
Targeting the calf muscles is much easier than targeting some other muscle groups of the lower leg.
However, certain exercise are better than other at targeting this muscle. The soleus works with only one joint (the ankle) and is best targeted by exercises with the legs bent. Exercises like the seated calf raise and the machine seated calf raise (or any calf raise you perform with the knee bent to about 90-degrees) are best for targeting this area of the calf.
The best way for getting bigger & stronger calves is by following our calf training tips!
Best ways to stretch soleus muscle
- Floor board bent-knee calf stretch
- Lunging bent-knee calf stretch
- Pike bent-knee calf stretch
- Kneeling calf stretch
- Floor-seated bent-knee calf stretch
- Floor-seated bent-knee towel calf stretch
- Step bent-knee calf stretch
- Wall bent-knee calf stretch
Self myofascial release techniques
- Foam roller
- Lacrosse ball. Here’s how you can use a lacrosse ball to release your calves.
- Sprinter stick. Here’s how to use “sprinter stick” to release your calves.
